The present invention relates generally to ophthalmic refractive laser surgery systems and more particularly to a device for actively controlling movement and position of both of the eyes during ophthalmic refractive laser surgery.
Lasers, such as UV (ultraviolet) or IR (infrared), are utilized in ophthalmic surgery to ablate the cornea of the eye in order to correct for abnormal conditions of the eye. Such lasers remove tissue from the cornea to reshape the surface of the cornea for refractive correction or for therapeutic surgery. Conventionally, when using laser devices, there is a fixation object for a patient to fixate an eye undergoing treatment upon during the surgery. Such fixation object typically takes the form of a blinking light source or an image of a light source. The fixation object is co-linear with the path of the laser beam and the line of sight or the visual axis of the eye being treated. In this manner, the eye being treated will remain steady by looking at the fixation object. During surgery the laser beam will be continuously ablating the cornea along the visual axis of the eye being treated.
Although such conventional fixation device has been useful there are several disadvantages associated with its use. One such disadvantage is that the patient undergoing treatment may not have full vision in the eye being treated and will not be able to see the fixation light. In particular, the surface of the cornea of the eye being treated is usually not a smooth surface due to the laser treatment or due to the removal of the flap during an LASIK procedure which prevents the patient from having full vision. Additionally, the patient can completely lose sight of the fixation object. In this case, the patient can become anxious and attempt to search for the fixation object which can cause the eye to move irregularly resulting in a poor outcome of the surgery.
Another disadvantage is that the fixation object is immobile which causes the treated eye to tire easily and to move off center. When this occurs the eye is no longer in fixation and again effective treatment may not result due to the movement of the eye being treated.
When the fixation object is a light source, the light can be reflected by the patient's eye. This reflected light enters the surgeon's eye through optics associated with a viewing microscope. This causes the surgeon to see a bright image of the fixation light on the eye of the patient. The reflected image can distract the surgeon and also impair the judgment of the surgeon during surgery.
Another problem associated with the use of a conventional fixation object is that the laser beam, the fixation light, and the microscope are not exactly co-axial with each other. When not in alignment, the patient's eye is not perpendicular to the laser beam. This may result in the patient's eye not being centered on the fixation object and misalignment of the laser beam.
A further problem may occur in the situation where an eye tracking system, such as an CCD camera, is being used during ophthalmic laser surgery to track movement of the eye undergoing treatment. In this situation, the laser beam is responsive to the eye tracking system to follow the movement of the eye as it shifts off center. The laser beam is adapted to always ablate centrally, however, the laser beam is now no longer collinear with the visual axis of the eye or normal to the surface of the eye. In this situation, the laser beam may ablate the wrong area of the cornea which results in not reshaping the cornea correctly.
The present invention is designed to obviate and overcome many of the disadvantages and shortcomings experienced by using a fixation object or target with the eye undergoing treatment, and to provide a device for actively controlling and positioning the eyes during refractive laser surgery. The present invention is intended to eliminate any unintended movement of the eyes undergoing treatment and to provide a device which assists accurate positioning of the eye prior to and during use of a laser to ablate the surface of the eye. There exist a need to provide an improved device for precisely aligning a laser beam before and during laser surgery while reducing movement of an eye undergoing treatment.